by Andre Leibovici

VDI Steady State Workload with VNX FAST Cache [Video]

Last week I published the first of a series of videos that I have been recording for use by the EMC vSpecialist team. The videos are focused on VDI and EMC technology. The first one was VDI Bootstorm with VNX FAST Cache [Video].

This is the second video and it validates VNX FAST Cache ability to promptly decrease Total Disk Utilization and Response Time during Steady State VDI workloads. If you would like to know more about how FAST Cache works I suggest the reading my article EMC FAST Cache effectiveness with VDI.

For this demo I decided to build a rather small VMware View environment with only 20 VMware View Linked Clones. You will then say — only twenty? — Yes, but those 20 virtual desktops are backed by only three SAS 15K drives.

In a typical VDI environment where pattern range around 20% reads and 80% writes random IOs, those three drives combined into a RAID5 group will support roughly 183 IOPS. This provides approximately 9.15 IOPS per virtual desktop.

The Medium VDI workload produced by LoginVSI is around 13 IOPS per virtual desktop. Consequently, the configuration is short on number of spindles required and will run into latency, affecting the response time and utilization. To avoid latency with 20 or 200 virtual desktops the number of spindles would have to be enough to support the workload appropriately.

Enter FAST Cache, and the disk LBA blocks with high number of access are dynamically and real-time promoted to a pair of SSD in RAID 10 configuration. According to my tests the same single pair of SSD would be enough to support a Steady State workload of 500 virtual desktops. I will soon publish an article where I explain the 500 scenario.